CN105068561A - Method and apparatus for actuation of a two-axis MEMS device using three actuation elements - Google Patents

Abstract

Apparatus and methods are provided for driving a two-axis MEMS mirror using three non-contact actuation elements or electrodes. A differential bi-directional mirror control uses unipolar drive voltages biased at a suitable value. Transformation functions map two-axis tip-tilt commands to three actuation drive signals for selected electrode orientations and sizes.

Description

Three driving elements are utilized to drive the method and apparatus of biaxial MEMS device

The cross reference of related application

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Background of invention

The present invention relates to the driving of MEMS (micro electro mechanical system) (MEMS) device, particularly relate to the driving of two-axis tip inclination (tip-tilt) MEMS mirror.The present invention can be applicable to electrostatic driven optical switch, but is not limited to this.

Utilize four driving elements with electrostatic type of drive and Magnetic driving mode to drive the scheme of two-axis tip inclination MEMS mirror to be well-known.Four component structures have the advantage about orthogonal tip-tilt axle straight-forward symmetry, and the transforming function transformation function therefore between tilted alignment (orientation) and the voltage applied each driving element or electric current is simpler and clearer.The driving method of common employing four electrodes is driven the paired electrode of axis homonymy, tilts relative to axis to make it.

In order to realize the control to single driving element, each element all needs himself voltage or electric current supply line and relevant driving circuit thereof.For the situation of photoswitch adopting the array of mirror closely separated, adopt a large amount of supply lines and driving circuit can the design of restriction system.Due to the constraint of encapsulation, along with the increase of MEMS number in array, then the cloth of these supply lines is configured to the challenge to system.And, along with the increase of driving circuit number, due to a large amount of electronic component of needs, so the cost scales of system increases.Therefore, need so a kind of scheme, it can reduce the number of driving circuit and supply line, thus minimizing is interconnected problem and driving problems.

Summary of the invention

According to the present invention, provide a kind of three noncontact driving elements or electrode of utilizing to drive the method and apparatus of two-axis MEMS mirrors.Differential two-way mirror controls to utilize to be biased and realizes with three of appropriate value actuation drive signals.Transforming function transformation function is utilized to be three actuation drive signals for selected electrode orientation and size by two-axis tip-tilt commands mapping transformation (map).

What propose here utilizes the theoretical foundation of three electrodes to can be applicable to other situation in electrostatic drives, and comprise two-axis tip-tilt device, it contains the electromagnetic driver for MEMS.Therefore, be to be understood that the present invention discloses, utilize three electrodes to drive two-axis tip-tilt device.

By the detailed description carried out below in conjunction with specific embodiments, the present invention will be made to obtain better understanding.

Brief description of drawings

Fig. 1 is the stereographic map of biopsy cavity marker devices, which depict the relative positioning according to two-axis MEMS mirrors array of the present invention and three drive electrodes.

Fig. 2 is the vertical view of biaxial MEMS mirror of the present invention and three drive electrodes, and wherein the axle of hinging device is directly aimed at electrode.

Fig. 3 is the vertical view of biaxial MEMS mirror of the present invention and three drive electrodes, and wherein the axle of hinging device is aimed at randomly with electrode.

Detailed description of the present invention

See figures.1.and.2, which show an embodiment of the MEMS mirror 4 be positioned among by the array 10 of three equivalent actuation elements 1,2 and 3 driving.When the mirror with two gimbal as shown in the figure, outside hinging device (hinge) 5 and 6 makes outer shroud and mirror can rotate around y-axis, and inner hinges 7 and 8 makes mirror 4 can rotate around x-axis, wherein x-axis and y-axis are all positioned at mirror 4 plane.For this specific embodiments of the present invention, the gap 9 between x turning axle with element 1 and 2 is aimed at, and element 3 is pointed in direction.In another embodiment of the present invention, as shown in Figure 3, the relative orientation of driving element and hinging device axle rotated one arbitrarily angled.In all embodiments of the present invention, the power driving mirror to tilt is provided by three driving elements 1,2 and 3.This power obtains by various device, comprises electrostatic equipment and magnetic device.In the electrostatic case, element 1,2,3 can be flat metal electrode.As mentioned below, by applying voltage to each electrode, producing electrostatic force between the conductive layer (not shown) (comprising mirror surface self) in electrode and mirror 4, causing mirror 4 to be tilted over a controllable angle.In the magnetic case, element 1,2,3 can be the circular coils of conductive traces of plane.By applying electrical current to each coil by current source, can be formed and the interactional magnetic field of ferromagnetic region (not shown) in mirror 4 (comprising mirror material self), thus induction produces interactional magnetic force, causes mirror 4 to tilt.

Driving element need not have equal area, and in other words, for identical drive singal, they need the power producing equal sizes.Therefore, in the another embodiment of the present invention in claims, in three driving elements, have at least important (significant) parameter of one to be different from other two.They can be different in a lot, including, but not limited to, area, shape and thickness.

Main aspect of the present invention is a kind of method, and by the method, the inclination of mirror can utilize three driving elements to control.Owing to having two separate rotational axes, so need two independently command signals.These command signals are respectively defined as V _xand V _y, it is respectively used to the rotation controlled around x-axis and y-axis.The key of problem be to determine how to come uniquely by command signal mapping transformation (map) to being denoted as V ₁, V ₂and V ₃three drive singal.Selected voltage source or current source can be come to generate these signals according to the type of driving mechanism.Mapping transformation can be represented by following linear system of equations usually:

V ₁＝AV _x+BV _y+V _f1，

V ₂=CV _x+ DV _y+ V _f2, and

V ₃＝EV _x+FV _y+V _f3，

Wherein, A, B, C, D, E, F, V _f1, V _f2and V _f3be all and V _xand V _yirrelevant constant.The mapping methods of arbitrary number can be realized.But not all method all can produce identical control characteristic.Therefore, problem is subject to following constraint, so that following characteristic is kept by mapping transformation:

(1) command signal V _xonly close with the significance bit phase shift of MEMS around x-axis.

(2) command signal V _yonly close with the significance bit phase shift of MEMS around y-axis.

(3) command signal V _xdifferential (differential), to make not change the average drive signal of three elements.

(4) command signal V _ydifferential (differential), to make not change the average drive signal of three elements.

Constraint condition (1) and (2) guarantee between two independent sense of rotation, there is not or seldom have cross jamming (cross-talk) cross (talk).Constraint condition (3) and (4) make system to command signal V _xand V _yresponse linearization.These two kinds of characteristics greatly simplifie feedback circuit or algorithm required in closed loop (closed-loop) operation of mirror.

By using constraint condition (1)-(4), the relativeness between constant A, B, C, D and E receives necessary constraint, that is, they can not be assumed that arbitrary value again.Their value also depends on the concrete structure configuration of driving element and the sloping shaft relative orientation about driving element.In the embodiment that Fig. 1 and Fig. 2 describes, all identical and orientation of three elements as shown in the figure, always keeps to make constraint condition (1) setting up, then need A and C's and with E linearly.Always keep to make constraint condition (2) setting up, then need B to equal D.That constraint condition (3) implication table understands A, C and D and equal zero, constraint condition (4) then implication table understand B, D and E and equal zero.All these constraint conditions all must meet simultaneously.Want to meet these constraint condition, then F must equal-2B simultaneously, and C must equal-A, and E must equal zero.Therefore, the generalized equation group of mapping transformation is simplified as following equations group, and it is denoted as M ₁:

V ₁＝AV _x–(F/2)V _y+V _f1，

V ₂=– AV _x– (F/2) V _y+ V _f2, and

V ₃＝FV _y+V _f3

System of equations M ₁how mapping transformation is three drive singal to have defined twin shaft command signal.Bias value V _f1, V _f2, V _f3can numerical value equal, or wherein one or more can be different from other value.Mapping transformation M ₁be applied to following situation, wherein three driving element profiles are all identical with shape, and spacing distance is equal, and relative to sloping shaft orientation as shown in Figure 2.Will be understood that M ₁mapping transformation is unique for element labeling system as depicted in figs. 1 and 2, and is also unique for the selection of the axes orientation shown in this few width figure.Component labelling and axes orientation have the multiple permutation and combination using this mapping transformation, just at drive singal V ₁, V ₂and V ₃distribution and coefficient A and F sign on have trickle change.

Only when driving element relative to the orientation of hinging device with consistent shown in Fig. 2 time, just can use mapping transformation M ₁.Under normal conditions, the orientation of driving element need not consistent with shown in Fig. 2.Driving element can rotate relative to the direction by mirror hinge axis limit.Fig. 3 display driver element is in arbitrary orientation, and wherein rotation angle θ is defined as driving element and rotates turned over angle in the counterclockwise direction from position of orientation shown in Fig. 2.No matter the relative orientation of driving element how, is set up in order to ensure constraint condition (1)-(4), must to the mapping transformation correct from command signal to drive singal.This is realized by transformed coordinate system, and wherein new coordinate axis have rotated an angle θ relative to original coordinates axle.The final new mapping transformation relation obtained is described below by one group of new linear equation, and it is denoted as M ₃:

V ₁＝(ACos(θ)+(F/2)Sin(θ))V _x+(ASin(θ)-(F/2)Cos(θ))V _y+V _f1，

V2=(-ACos (θ)+(F/2) Sin (θ)) Vx+ (-ASin (θ)-(F/2) Cos (θ)) Vy+V _f2, and

V3＝-FSin(θ)Vx+FCos(θ)Vx+V _f3

Mapping transformation described by these equations is generalized form, and wherein electrode all has same size, relevant with the mirror 4 utilizing three driving elements 1,2 and 3 to control with two gimbal.Bias value V _f1, V _f2and V _f3can be all equal, also can be the value that wherein one or more value is not equal to other.

Of the present invention one more specifically embodiment provide the simplified version of mapping transformation.Mapping transformation a kind of desirable but nonessential characteristic be, when driving element turns over the angle of the integral multiple of 120 degree, mapping transformation pattern is constant.Because these three driving elements have symmetry, if so driving element is the integral multiple of 120 degree relative to the angle that mirror hinge turns over, then new structural allocation is equal to the structural allocation before not rotating completely, just some footy change of mark of driving element.For making mapping transformation remain unchanged, except making the footy arrangement of mark 1,2,3, also the ratio of constant A and constant F must be defined as and equal like this, represented by following system of linear equations the mapping transformation of a kind of particular type that the present invention predicts, it is denoted as M ₄:

$V_1=F\left(\right(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F\left(\right(\sqrt{3}/2)Sin\left(\mathrm{\θ}\right)-(1/2)Cos\left(\mathrm{\θ}\right))V_y+V_f,$

$V2=F(-(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F(-(\sqrt{3}/2)Sin\left(\mathrm{\θ}\right)-(1/2)Cos\left(\mathrm{\θ}\right))V_y+V_f,$

V3＝-FSin(θ)V _x+FCos(θ)V _x+V _f

This unique mapping transformation just, had both met constraint condition (1)-(4), met again the requirement that when driving element turns over the angle of the integral multiple of 120 degree, mapping transformation pattern is constant.Mapping transformation M ₄be only applicable to driving element be mutually equal to as shown in Figure 3 and the situation arranged at equal intervals.

The present invention carries out elaboration explanation in conjunction with specific embodiments.But for those of ordinary skills, adopt other embodiment to be also apparent.Such as, the present invention is not limited in the mirror with two gimbal.From describing above, the different relative orientation of mirror axle and three electrodes is also allow, and it causes the coefficient in the mapping transformation between two differential instructions (differentialcommands) and three electrode commands different.Therefore, should not understand the present invention with limitation sight, the present invention is limited only by the accompanying claims.

Claims (13)

1. controlledly can carry out a device with two axles for two-way angular displacement, comprise:

Platform, it can respond and drives and carry out angular displacement around described two axles;

First, second, and third electrostatic attraction electrode, it is positioned near described platform, described three electrodes are only utilized to provide direct contactless driving for described platform, the center of at least two electrodes in described electrode separates, in order to realize effective two-way angular displacement by each of carrying out two axles of angular displacement wherein said;

Three Control of Voltage sources, it controls the independence of three corresponding electrostatic force for providing to described first, second, and third electrode; And

Controller, for will be described three electrostatic force relative to the described select location mapping transformation carrying out two axles of angular displacement.

2. device according to claim 1, wherein, two electrodes in described electrode have and the unequal area of the first electrode in described electrode.

3. device according to claim 1, wherein, first electrode in described electrode is arranged to first axle directly aimed in described axle, and described second electrode and the 3rd electrode are arranged on the relative both sides of described first axle in described axle respectively symmetrically.

4. device according to claim 1, wherein, described electrode has unequal area, and is configured to the gap between described electrode is not coincided with described axle.

5. device according to claim 1, wherein, described platform can also along the z-axis displacement substantially vertical with the plane of the platform be not biased, thus described platform moves along z-axis in the mode moved back and forth.

6. device according to claim 1, wherein, described control device according to following relational operation to carry out mapping transformation:

$V_1=F\left(\right(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F$

$\left(\right(\sqrt{3}/2\left)Sin\right(\mathrm{\θ})-(1/2\left)Cos\right(\mathrm{\θ}\left)\right)V_y+V_{f1},$

$V_2=F(-(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F$

$(-(\sqrt{3}/2\left)Sin\right(\mathrm{\θ})-(1/2\left)Cos\right(\mathrm{\θ}\left)\right)V_y+V_{f2},$ And

V ₃＝-FSin(θ)V _x+FCos(θ)V _x+V _f3

Wherein, F and bias value V _f1, V _f2and V _f3be all and angular displacement command signal V _xand V _yirrelevant constant; And

Wherein, described electrode has equal area, and the described mapping transformation when center z-axis rotates the angle of the integral multiple of 120 degree of described electrode is constant.

7. device according to claim 1, wherein, all described electrodes have equal area, and are configured to the gap between described electrode is not coincided with described axle.

8. for carrying out a method for Linear Control to the device with two axles that controlledly can carry out two-way angular displacement, described device comprises: platform, and it can respond and drives and carry out angular displacement around described two axles; Three electrodes, it is positioned near described platform, for providing direct contactless driving for described platform, the center of at least two electrodes in described electrode separates, in order to provide effective two-way angular displacement in the angular range of maximum possible by each of carrying out two axles of angular displacement wherein said; Only three Control of Voltage sources, it is for providing independently control to described three electrodes; And controller, for being three controls relative to the described select location mapping transformation carrying out two axles of angular displacement, said method comprising the steps of:

Select the displacement angle of described platform;

The angle map of described displacement is transformed to the angle command carrying out displacement around x-axis and y-axis;

According to the mapping function of specifying, described two angle command are transformed to only three bias values from first and second controllable angle map, for generation angle induction electrode voltage instruction, described voltage instruction is used for directly not controlling first and second controllable angle described with the mode of described contact with platform; And

Described angle induction electrode voltage instruction is applied, to change the angular displacement of described platform on the basis of first and second controllable angle described for electrostatically to described three the control sources for described electrode.

9. method according to claim 12, wherein, described controller ties up to the electrode voltage V in described three Control of Voltage sources according to following pass ₁, V ₂and V ₃between carry out mapping transformation:

V ₁＝AV _x+BV _y+V _f1，

V ₂=CV _x+ DV _y+ V _f2, and

V ₃＝EV _x+FV _y+V _f3，

Wherein, A, B, C, D, E, F and bias value V _f1, V _f2and V _f3be all and angular displacement command signal V _xand V _yirrelevant constant.

10. controlledly can carry out a device with two axles for two-way angular displacement, comprise:

Platform, it can respond and drives and carry out angular displacement around described two axles;

First, second, and third electrostatic attraction electrode, it is positioned near described platform, for providing contactless driving for described platform, the center of at least two electrodes in described electrode separates, in order to realize effective two-way angular displacement by each of carrying out two axles of angular displacement wherein said;

Three Control of Voltage sources, it controls the independence of three corresponding electrostatic force for providing to described first, second, and third electrode; And

Controller, for being described three electrostatic force relative to the described select location mapping transformation carrying out two axles of angular displacement, described controller ties up to the electrode voltage V in described three Control of Voltage sources according to following pass ₁, V ₂and V ₃between carry out mapping transformation:

V ₁＝AV _x+BV _y+V _f1，

V ₂=CV _x+ DV _y+ V _f2, and

V ₃＝EV _x+FV _y+V _f3，

Wherein, A, B, C, D, E, F and bias value V _f1, V _f2and V _f3be all and angular displacement command signal V _xand V _yirrelevant constant.

11. devices according to claim 10, wherein, described first electrode is arranged to first axle directly aimed in described axle, and described second electrode and the 3rd electrode are arranged on the relative both sides of described first axle in described axle respectively symmetrically.

12. 1 kinds of devices with two axles that controlledly can carry out two-way angular displacement, comprising:

Platform, it can respond and drives and carry out angular displacement around described two axles;

First, second, and third electrostatic attraction electrode, it is positioned near described platform, for providing contactless driving for described platform, the center of at least two electrodes in described electrode separates, in order to realize effective two-way angular displacement by each of carrying out two axles of angular displacement wherein said;

Three Control of Voltage sources, it controls the independence of three corresponding electrostatic force for providing to described first, second, and third electrode; And

Controller, for will be described three electrostatic force relative to the described select location mapping transformation carrying out two axles of angular displacement, wherein said control device according to following relational operation to carry out mapping transformation:

V ₁＝(ACos(θ)+(F/2)Sin(θ))V _x+(ASin(θ)-(F/2)Cos(θ))V _y+V _f1，

V ₂=(-ACos (θ)+(F/2) Sin (θ)) V _x+ (-ASin (θ)-(F/2) Cos (θ)) V _y+ V _f2, and

V ₃＝-FSin(θ)V _x+FCos(θ)V _x+V _f3

Wherein, A, F and bias value V _f1, V _f2and V _f3be all and angular displacement command signal V _xand V _yirrelevant constant,

Wherein, described electrode has equal area, and is configured to the gap between described electrode is not coincided with described two axles.

13. 1 kinds of devices with two axles that controlledly can carry out two-way angular displacement, comprising:

Platform, its can respond drive and around described two axle reorientations;

First, second, and third driving element, it is positioned near described platform, for providing contactless driving for described platform;

Three control source, and it is for providing independently control to described first, second, and third driving element; And

Controller, for will be three controls relative to the described select location mapping transformation carrying out two axles of angular displacement according to following relation:

$V_1=F\left(\right(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F\left(\right(\sqrt{3}/2)Sin\left(\mathrm{\θ}\right)-(1/2)Cos\left(\mathrm{\θ}\right))V_y+V_{f1},$

$V_2=F(-(\sqrt{3}/2)Cos\left(\mathrm{\θ}\right)+(1/2)Sin\left(\mathrm{\θ}\right))V_x+F(-(\sqrt{3}/2)Sin\left(\mathrm{\θ}\right)-(1/2)Cos\left(\mathrm{\θ}\right))V_y+V_{f2},$

V ₃＝-FSin(θ)V _x+FCos(θ)V _x+V _f3

Wherein, F and bias value V _f1, V _f2and V _f3be all and angular displacement command signal V _xand V _yirrelevant constant; And

Wherein, described driving element has equal area, and the described mapping transformation when center z-axis rotates the angle of the integral multiple of 120 degree of described driving element is constant.